Direct observations of epitaxial growth

The technique of in situ transmission electron microscopy has made a major contribution to the understanding of the processes responsible for nucleation, growth and defect structures of epitaxial thin films. Early work with this technique was heavily criticized because it was carried out under poor vacuum conditions, but in recent years many of these criticisms have been overcome as a result of studies performed in greatly improved vacuum environments. As a result of these improvements, it is now possible to extend the ranges both of substrate materials and of evaporants. The main object of this review is to summarize the instrumental developments and the impact that this technique has made in the epitaxy field. The advantages and disadvantages of the method will be emphasized and areas which might be fruitfully studied in the future will be discussed.